Afternoon media screenings are usually sedate affairs, respectably quiet and even a little snoozy, which is why it was such a jolt when the jagoff behind me started yelling at the screen at the end of Errol Morris’ The Unknown Known. His outburst was in response to the final question that Morris asks his subject, former Secretary of Defense Donald Rumsfeld. The question: “Why are you doing this? Why are you talking to me?” The infuriated response from behind me: “Because you ask SOFTBALL QUESTIONS!” (That’s actually a guess; he mumbled the first few words of his outburst, which I should accurately transcribe as “Garble garble SOFTBALL QUESTIONS!”) The credits rolled, and the heckler marched out, so I didn’t get a chance to ask him what, exactly, he was expecting. Had he not seen an Errol Morris film before? Because this is not a filmmaker who grills people. That’s not really his thing. Instead, he poses simple questions and lets them talk, and talk, and talk. In doing so, he gives them enough rope to hang themselves — either via their own rhetorical fumbles, or by editing in such a way as to undercut them. That’s what he does in The Unknown Known. And it works.

Rumsfeld laughs off that last question, but there is a clear answer to it: he talked to Morris because of The Fog of War. The Unknown Known is the closest thing Morris has ever made to a sequel, following in the spirit and style of his 2003 documentary profile of another controversial and much-reviled Secretary of Defense, Robert McNamara. That picture won Morris an Oscar and McNamara a reconsideration; his part in the escalation of the Vietnam War certainly wasn’t forgiven, but he comes off as something of an elder statesman, sharp as a tack, cognizant of (and just shy of apologetic for) his mistakes, and keenly aware of how his successors were making many of the same ones.

Rumsfeld isn’t quite so lucky. To be sure, Morris presents Rumsfeld as thoughtful and intelligent; his memories are crisp (when he wants them to be), and he makes the occasional valid point (like his sly jab at the policies and practices from the Bush administration that Obama has kept in place). He’s a good storyteller — witness his vivid remembrances of an assassination attempt on President Ford, or his first meeting with Sadaam Hussein back in ’83 — and the man is even, swear to God, sympathetic in spots.

But that shouldn’t come as a surprise. It’s easier, for us and frankly for them, to dismiss those whose politics and policy decisions we abhor as monsters or Bond villains and leave it at that. What’s more interesting — in our interactions, and in our understanding of history — is to understand how smart people can make giant miscalculations, and dig in their heels.

Over the course of The Unknown Known, it becomes clear that Rumsfeld sleeps at night via a potent brew of delusion and semantics. Early on, Morris adopts a new visual gimmick to accompany his customary moody reenactments, askew stock footage, and giant close-ups of text: a background graphic of dictionary definitions for key words in Rumsfeld’s answers. It’s used sparingly, and initially, it seems, as a bit of a gag. But the more time we spend with Rumsfeld, the more we understand that this is a man who spends copious amounts of time parsing words. Morris uses, as an organizing principle, the many, many (so many that they are dubbed “snowflakes,” and many days were blizzards) memos that he issued, working documents that became a kind of diary. At one point, Morris cuts together a series of them, in which the subject line is “definition,” in which he asks his staff and colleagues to provide “dictionary definitions” of words they are using and shouldn’t, or are using incorrectly: terrorism, guerrilla warfare, unconventional warfare, insurgency, victory, scapegoat. When Morris brings up torture, Rumsfeld talks in circles; he insists we don’t assassinate, and dismisses assassination attempts as “acts of war”; he stands by his declaration, in 2002, that the Geneva convention doesn’t apply to detainees, because “detainees are not POWs.” When language damns your behavior, in other words, challenge the language.

But sometimes that’s not enough, and one must simply fool oneself. In discussing Abu Ghraib, Rumsfeld denies the idea of a “migration” of attitudes and techniques from Gitmo to Abu Ghraib, and cites the Schlesinger report — from which Morris reads back to him a quote stating that’s exactly what happened. When Morris brings up the conflation of Saddam Hussein and 9/11, Rumsfeld insists, “I don’t think the American people were confused about that.” When Morris cites polls indicating that, no, they sure were, Rumsfeld replies, “I don’t recall anyone in the Bush administration saying that.” And like magic, Morris cuts to Rumsfeld, in 2003, saying exactly that.

So how, in the years since the invasion of Iraq, has Rumsfeld convinced himself that he said and did the exact opposite of what he actually said and did? We can only guess. But it’s possible to make some conclusions from how he looks outside of himself, at others — like Hussein’s Deputy Prime Minister Tariq Aziz, of whom he notes, “You wonder what goes on in a mind like that?” Or better yet, Hussein himself, about whom Rumsfeld remembers, “He was living his image of himself, which was pretend.” Rumsfeld says this in a closeup, at the end of an observation, but Morris doesn’t cut away. He keeps his camera on Donald Rumsfeld, and holds. And holds. And holds.